1. Field of the Invention
The present invention relates to a centrifugal clutch allowing smooth, convenient shifting of gear.
2. Description of the Related Art
A centrifugal clutch is generally used in a beach car or other vehicles. FIG. 5 of the drawings illustrates a conventional centrifugal clutch comprising a driving wheel 1xe2x80x2, an operative disc 2xe2x80x2, a transmission disc 3xe2x80x2, and a follower shaft 4xe2x80x2. The driving wheel 1xe2x80x2 is driven by an engine (not shown) via a belt 11xe2x80x2. The driving wheel 1xe2x80x2 includes a central hole 12xe2x80x2 for receiving a bearing 13xe2x80x2 through which the follower shaft 4xe2x80x2 extends. A side of the driving wheel 1xe2x80x2 includes an engaging portion 14xe2x80x2 to which a nut 15xe2x80x2 is threadedly engaged.
The operative disc 2xe2x80x2 includes a central hole 21xe2x80x2 through which the follower shaft 4xe2x80x2 extends, thereby securely engaging with the driving wheel 1xe2x80x2 to move therewith. The operative disc 2xe2x80x2 further includes plural pivotal blocks 22xe2x80x2 on an outer periphery thereof. Each pivotal block 22xe2x80x2 has an end pivoted to the operative disc 2xe2x80x2 and a friction plate 23xe2x80x2 on an outer side thereof. Each pivotal block 22xe2x80x2 is attached to the operative disc 2xe2x80x2 by a spring 24xe2x80x2. In a normal state, each pivotal block 22xe2x80x2 is received in the operative disc 2xe2x80x2 under the action of the associated spring 24xe2x80x2.
The transmission disc 3xe2x80x2 is mounted to the outer periphery of the operative disc 2xe2x80x2 and includes an engaging portion 31xe2x80x2 for frictional engagement with the pivotal blocks 22xe2x80x2 to move therewith. The transmission disc 3xe2x80x2 further includes a central hole 32xe2x80x2 for engaging with the follower shaft 4xe2x80x2 to move therewith.
The follower shaft 4xe2x80x2 extends through the driving wheel 1xe2x80x2, the operative disc 2xe2x80x2, and the transmission disc 3xe2x80x2. An end of the follower shaft 4xe2x80x2 includes teeth 41xe2x80x2 and a threaded portion 42xe2x80x2. The teeth 41xe2x80x2 of the follower shaft 4xe2x80x2 mesh with teeth 33xe2x80x2 in the central hole 32xe2x80x2 of the transmission disc 3xe2x80x2, and a nut 43xe2x80x2 is engaged with the threaded portion 42xe2x80x2 for positioning purpose. A coupling device 5xe2x80x2 is mounted to the follower shaft 4xe2x80x2 and includes a coupling block 51xe2x80x2 and a gear 52xe2x80x2 that is connected to a gear train (not shown) in a gearbox (not shown) of a vehicle. The coupling block 51xe2x80x2 includes plural protrusions 511xe2x80x2 on a side thereof. The gear 52xe2x80x2 includes plural recesses 521xe2x80x2 for releasable engagement with the protrusions 511xe2x80x2, thereby allowing joint movement of the gear 52xe2x80x2 and the coupling block 51xe2x80x2.
In an idle state, the engine drives the driving wheel 1xe2x80x2 to run at the idling speed, which, in turn, causes rotation of the operative disc 2xe2x80x2, but the follower shaft 4xe2x80x2 is not turned. When the operator shifts from the idle state to a gear, as illustrated in FIG. 6, the engagement between the protrusions 511xe2x80x2 of the coupling block 51xe2x80x2 and the recesses 521xe2x80x2 of the gear 52xe2x80x2 would not be smooth when they are not aligned with each other.
Referring to FIG. 7, when the operator accelerates to turn the operative disc 2xe2x80x2 at a high speed, each pivotal block 22xe2x80x2 pivots outward as a result of centrifugal force. Thus, the friction plates 23xe2x80x2 engage with the engaging portion 31xe2x80x2 of the transmission disc 3xe2x80x2 to thereby move jointly. The transmission disc 3xe2x80x2 turns to drive the follower shaft 4xe2x80x2 at a high speed, thereby moving the vehicle. When gear shifting is proceeded at this high speed, the protrusions 511xe2x80x2 of the coupling block 51xe2x80x2 would impact the gear 52xe2x80x2. Damage is caused accordingly.
An object of the present invention is to provide a centrifugal clutch allowing smooth, convenient shifting of gear.
A centrifugal clutch in accordance with the present invention comprises a driving wheel, an operative disc connected to the driving wheel to move therewith, a transmission disc mounted to an outer periphery of the operative disc, a follower shaft, a friction mechanism, and a coupling device for releasable coupling with a gear train of a gearbox.
The driving wheel includes an engaging portion on a side thereof, the engaging portion including a friction portion. The operative disc includes plural pivotal blocks on the outer periphery thereof. Each pivotal block includes an end that is pivoted to the operative disc and has a friction plate on an outer side thereof. The transmission disc includes an engaging portion for frictional engagement with the pivotal blocks to move therewith. The follower shaft extends through the driving wheel, the operative disc, and the transmission disc. The follower shaft is securely engaged with a central portion of the transmission disc to turn therewith. The operative disc is turned together with the driving wheel. Each pivotal block is moved to a position for frictional engagement with the transmission disc when the operative disc turns at a high speed, thereby driving the transmission disc and the follower shaft to turn. The friction mechanism is fixed to the transmission disc and in frictional engagement with the friction portion of the driving wheel.
When the driving wheel turns at an idling speed, the friction portion drives the friction mechanism, the transmission disc, and the follower shaft to turn slowly with a constant torque, thereby allowing easy gear shifting through the coupling device.